Interesting Physics beyond the QGP discovery phase Heavy flavor production Flavor dependence of QCD energy loss Jet studies and gluon-jet correlations in 4  Chiral Symmetry Restoration Onium Physics R. Bellwied, February 2002

Interesting physics in the SPS dilepton spectrum Dilepton Measurements: open charm production (D) charmonia suppression (J/  ) light mesons in dense matter (  ) thermal dimuons from QGP Charm is a heavy flavor that is abundantly produced at RHIC so These measurements provide the closest link to pQCD, together with jet production at RHIC

No enhancement in pp and pA collisions Strong enhancement of low-mass e + e - pairs in A-A collisions (compared to expected yield from known sources) Enhancement factor (.25 <m<.7GeV/c 2 ) : 2.6 ± 0.5 (stat) ± 0.6 (syst) Low Mass Electron Pairs: Chiral Symmetry Restoration ? (measure leptonic and hadronic decay channels)

The Intermediate Mass Region (IMR) excess: evidence from SPS (NA38/NA50) pA: AA: NA38+NA50 Properly described by Drell-Yan and D meson decays and with a Total charm cross- section consistent with previous direct measurements IMR yield is higher than the sum of DY and D meson decays in particular A factor 2 higher in central Pb-Pb

Possible explanation for IMR excess Thermal radiation ? Very good fit to data but is a factor 3 charm enhancement conceivable ? Good account for the IMR excess when added to expected sources assuming QGP phase with T i = 192 MeV Measure Charm Enhancement at RHIC direct via hadronic decay channels

PHENIX Single Electron Spectra

PHENIX Single Spectra Result

PHENIX Charm Yield Estimate

PHENIX Charm Yield Comparison No Charm Enhancement necessary to explain RHIC data ?

A high precision vertex detector will allow a clean separation of charm and bottom decays m c   eX GeV  m % D  6.75 D ±  17.2 B  5.3 B ±  5.2 Need secondary vertex resolution ~ m m We need a direct measurement of heavy flavor production

m c  GeV  m prime decay channel D  K - + anything (54%), K -  + (4%) D ±  K -  +  + (9%),K 0  + (3%) B  K* J/  B ±  K + J/  CDF (Phys. Rev. D58 (1998) ) very successful in direct B-meson reconstruction using new defined isolation cut. Decay channels for direct measurement D’s are relatively abundant (higher yield in STAR detector than  1D/unit y)) Even B-mesons be in our acceptance ~ once every ~100 events

Flavor dependence of QCD energy loss Prediction by X.N.Wang et al. Phys.Rev.C 57 (1998) 899

Study flavor dependence of jet quenching (tag with identified high p T particle) Important to extend spectra of identified charged particles out to as high p T as possible Enhanced High p T Physics

Flavor dependence of energy loss Prediction by X.N.Wang,Phys.Rev.C 58 (1998) 2321

pt-dependence of ratios in STAR (based on year-1 data) Need high pt !! (will get a little more from statistics in years-2+ (based on existing RICH for p and topology analysis for  )

How to measure a high pt spectrum For the primaries you need PID out to large pt (see next slide) For the secondaries you can use the topology method out to large pt without PID (to some extent). E.g. the  spectrum in STAR will reach out to about 5 GeV/c. You need precision tracking for D-meson and B-meson reconstruction.

Extended PID with Aerogel Aerogel together with TOF can extend the PID capability up to ~ 10 GeV/c n=1.007Aerogel n=1.004RICH  ~100 ps TOF Kaon-Proton separation Pion-Kaon separation Y. Miake

Forward Physics in STAR l Charged hadron and lepton (?) spectra (pt and rapidity) between h = for AA and pA collisions. l Separate peripheral collision program l Important jet physics program in pp and pA. l V0 reconstruction (without PID) l Possibly better phase space for D-meson mass reconstruction through charged hadron channel Bellwied, RHIC workshop

More Forward Physics Goals Measurements in the baryon-dense regime l In central collisions the forward region will be baryon-rich (high baryochemical potential). Exotic phenomena, e.g. centauro-like events and strangelets, are preferably produced in such an environment.. l production of light nuclei and antinuclei carries information of baryochemical potential and of production mechanism in baryon-rich region compared to baryon-poor mid-rapidity region. anti-proton suppression due to increased annihilation ? Bellwied, RHIC workshop

Precision Measurements: Tagged Jet quenching Direct  -tagged events: E  ~E jet Compare AA to pp Need to measure p T spectrum of particles opposite high E T   or  0 ? Need to do this vs Species/Energy to find energy loss How big? Proportional to mean free path? Gluon/quark difference P T Reaction Plane jet  Collision axis  Large back to back coverage: EMCAL and tracking & high pt pid in 4  would be ideal

Tomography? (penetrating probes) (from Richard Seto’s talk) Do as a function of “position” I.e. many bins of centrality, pt, y, reaction plane E.g Jet energy loss Mass shift Other? (J/  Suppresssion/charm enhancement) Requires Very High statistics E.g. 10 bin in pt, 5 bins in y,5 bins in centrality, 8 bins in reaction plane 400 points per centrality; 2000 points Good geometry measurements Reaction plane/centrality – event by event

Summary There is interesting physics in the heavy flavor production (s, c, b) that is not achievable with the present STAR detector. In particular the D- and B-meson cross section and the pt-spectrum of strange, charm and bottom particles ( flavor dependence of QCD energy loss) Jet studies and gluon-jet correlations will benefit from 4  coverage In terms of continuation of original measurements: Measure lepton and hadron decay channels of vector mesons in parallel (chiral symmetry restoration) -> Tomography of the QGP source

Detectors we need High pt PID in 4  RICH, Aerogel and TRD detectors High precision vertexing at central rapidity Active pixel or CDD layers High precision tracking in 4  Forward tracking with straw-tubes or Silicon -> See Howard’s Talk

Separation of charm/bottom decays by measuring displaced secondary vertex improve measurement accuracy of c and b cross sections to < 10% separate c and b contribution in each p T bin (flavor dependence of QCD energy loss) Direct measurement of D mesons combined with particle id, can measure D -> Kp modes => p T spectrum of D’s (flavor dependence of QCD energy loss) Improved momentum resolution for Upsilon spectroscopy Enhanced capabilities for spin physics wider acceptance (g-jet & jet-jet studies, c,b-tagging, etc) Enhanced physics capabilities for charm and bottom in pA Enhanced Physics Capabilities with a High Precision Vertex Tracker

PHENIX Background Subtracted Spectra